Use of helper-free retroviral vector to direct a high expression of porcine growth hormone in mouse fibroblast cells.

A retroviral vector has been employed to express the cDNA coding for porcine growth hormone (pGH) in the mouse fibroblast cell NIH 3T3 in large quantity. In this study, a single gene vector which contained no selectable marker was used. We have coinfected NIH 3T3 cells with pGH retrovirus and Neo(r) retrovirus to obtain a stable, high-expression clone. Using a superinfection strategy, we further increased the copy number of proviral DNA in the host chromosome, thus increasing the pGH secretion from 22 to 55 micrograms/10(6) cells/24 h. The recombinant pGH produced from mouse fibroblast cells was heterogeneous at the N-terminus, which mimicked the situation with bovine growth hormone either from natural sources or from recombinant products derived from mouse fibroblasts. This technology is useful for many biologically important genes to be stably transduced by retroviral vector into mammalian cells and highly expressed.     

Direct detection of circulating free radicals in the rat using electron spin resonance spectrometry.

We developed a new technique for directly observing in vivo free radical formation in the circulating blood of living rats using electron spin resonance (ESR) spectrometry without any labeling or trapping agents. It was found that a doublet peak spectrum was obtained following ferric citrate and ascorbic acid injection. The signals were confirmed in different ways to be due to ascorbic acid radicals. These results provide evidence to support the involvement of free radical intermediates in iron-ascorbic acid reactions, and further confirm the suggested mechanisms of both the adverse and protective effects of ascorbic acid in biological systems. Furthermore, this method of direct observation is a new application of ESR spectrometry to living animals.     

Technique for repeated collection of cerebrospinal fluid from cisterna magna of anesthetized strain 13 guinea pigs

To study biochemical changes in cerebrospinal fluid (CSF), we developed a reliable technique for repeated collection of CSF in anesthetized strain 13 guinea pigs. The animal's head was mounted in a stereotaxic instrument with ventral tilt at 30 degrees, and cisternal puncture was made with an L-shaped, 23-gauge needle through the shaved skin. Clear CSF was collected in a 1-ml syringe surrounded by crushed ice. Each collection procedure lasted for 3 min, and three consecutive collections produced about 0.2 ml of CSF. Sampling was repeated at 3-hr intervals. With intravenous saline infusion (10 ml/kg.hr), a total volume of 0.6-1.0 ml of CSF was collected over 6 to 12 hr. Animals maintained a mean blood pressure, heart rate, and minute volume, with few changes during CSF sampling for the entire collection.     

猫体感皮层神经元对同时刺激隐神经的A类和C类纤维的反应型式

记录了麻痹猫的体感皮层(SI)神经元的自发和隐神经的A类和C类纤维传入诱发放电(A-ED和C-ED)。用NCCVF分析神经元放电。结果表明,SI区神经元对同时刺激隐神经的A类和C类纤维的反应呈多种型式:(1)A-ED和C-ED共存,包括Ⅰ.A-ED和C-ED始终相互伴随出现;Ⅱ.在刺激之初,只出现A-ED,但是,当阻断A类纤维传入并由C类纤维传入诱发神经元放电后,再同时刺激A类和C类纤维时,A-ED和C-ED便同时出现。(2)A-ED制约C-ED,特点是,只要A-ED存在,C/ED就不出现。只有阻断A类纤维传入后,C-ED才产生。(3)单一A-ED,不管在什么刺激条件下,这类神经元都只有A-ED,而不产生C-ED 结论:根据反应型式的不同,可将SI区的神经元分为Ⅰ.A类和C类纤维传入同时驱动的神经元;Ⅱ.A-ED制约C-ED的神经元;Ⅲ.只由A类纤维传入驱动的神经元。     

毒黄素对黄嘌呤氧化酶作用的影响

利用从椰毒假单胞菌(Pseudomona cocovenenans)中所分离提取的毒黄素(toxoflavin)对黄嘌呤氧化酶(EC.1、2 3、2)作用的动力学试验表明,毒黄素是此酶的非必需激活剂,而且对以次黄嘌呤为底物的反应的激活作用明显高于以黄嘌呤为底物的反应。此激活作用属于部分混合型。这一结果为探寻毒黄素对人体的致毒机理提供了一条重要线索。     

美洲蜚蠊机械感受器输出信号的计算机分析

对蜚蠊单个机械感受器诱发反应峰电位的历程及幅度,使用系列分析、栅分析、时序分布、累加密度函数、栅—频分析、特征参数的伪三维隐线显示、峰电位幅度概率密度函数、峰电位间隔概率密度函数等分析方法,获得较多的神经信号间隔编码信息,以揭示刺激和反应之间的复杂关系。峰电位间隔和栅—频分析图由函数经曲线拟合后,分别求得描述其动态过程的时间常数τ_1,τ_2和τ_3,应用上述多种分析显示方法,使研究者更为直观地观察和定量描述刺激—反应间的动态关系。     

西双版纳傣族“龙山”的生态学意义

傣族“龙山”是西双版纳地区傣族的民族植物文化中的一例。其概念是“神居住的地方”,在这个地方的动植物都是神的家园里的生灵,是神的伴侣,是不能砍伐、狩猎和破坏的。人     

神农架拐棍竹林的初步研究

拐棍竹(Fargesia spathacea Franch.)是中国特有分布种类,主要分布川、滇、陕、甘等省。是极有开发价值的植物资源,又是大熊猫取食主要竹种之一。本文研究了神农架拐棍竹林的生态生物学特点,客观地估算了其蕴藏量,进行了营养成分分析。现报道如下:     

神农架金丝猴的生态学观察

金丝猴(Rhinopithecus roxellanae)仅产于我国,属国家Ⅰ级保护动物,自然分布于四川、陕西、甘肃的部分地区和湖北省神农架自然保护区。1983年以来,笔者对神农架金丝猴生存环境生态习性等作了长期观察研究,结果报道如下。